Most of conventional multilayer wiring boards are used in operating frequencies lower than 1 GHz. However, in recent years, in accordance with increase of an amount of information processed in electronic equipment, improvement of information processing capacity by downsizing and integration of a system, and, further, increase in information processing speed (realizing higher operating frequencies) have proceeded. In accordance with such trend, downsizing, higher density wiring, increase in the number of layers and adaptation to high frequencies (a lower transmission loss) are desired for multilayer wiring boards used in electronic equipment.
Particularly, as to adaptation to higher frequencies, it is requested to realize a lower transmission loss at an operating frequency of 1 GHz or higher (particularly, approximately from 1 to 3 GHz). To respond to such a request, while a high frequency-adaptive base material is used as a material for an insulating layer of the multilayer wiring board, there is a problem such as increase in cost due to use of the high frequency-adaptive base material.
Therefore, Patent Literature 1 discloses a multilayer wiring board which adapts to high frequencies at a relatively low cost by using a core material of a high frequency-adaptive base material in an outermost layer and using a general-purpose base material in an inner layer.